Multiplexing method and transceiver

ABSTRACT

The invention relates to a multiplexing method and a transceiver used in a TDMA radio system. The transceiver sets up a connection to another transceiver by transmitting modulated signals in time slots. The transceiver comprises coding means for channel-coding a signal that consists of bits and that is formed into a communication signal, and interleaving means for interleaving the bits of the channel-coded Signal into blocks of a predetermined size. The transceiver also comprises multiplexing means that receive blocks from the interleaving means and that multiplex the interleaved blocks of at least two channel-coded signals together. The transceiver further comprises modulation means for modulating the blocks multiplexed by the multiplexing means with at least four-level modulation before the modulated signal blocks are transmitted as a communication signal in a time slot, so that the transmission speed of the communication signal and the number of the connections to be established can be increased.

FIELD OF THE INVENTION

The invention relates to a multiplexing method used in a TDMA radiosystem, in which method connections are set up by means of signals thatare transmitted in time slots and that are modulated before thetransmission, and wherein a signal consisting of bits is received andchannel-coded into channel-coded signals each of which is interleavedinto blocks of a predetermined size.

BACKGROUND OF THE INVENTION

In digital radio systems, information can be transmitted by means ofbinary symbol sequences. Binary symbol sequences constitute a signal tobe transmitted, and the placement of binary symbol sequences in thesignal to be transmitted is called digital modulation. Digitalmodulation is carried out in practice by a digital modulator. In thesimplest form, the modulator places the binary symbol sequences in thesignal regardless of the blocks that have already been transmitted orthat will be transmitted later. The modulator may place the symbols inmultiple levels in the signal in order to form several differentwaveforms. The prior art teaches the use of for example the digital QPSKmodulation method as a multilevel modulation method.

In GSM systems, it is possible to use the TDMA multiple access methodwherein signals are transmitted in the form of bursts in time slots. Aspeech signal is coded into time slots by different coding methods. Aspeech signal is formed into blocks of for example 260 bits that arechannel-coded into signals of typically 456 bits. The channel-codedsignal is interleaved in order to decrease the effect of possibleinterfering signals on the information signal. The interleaving can becarried out for example such that the 456 bits are divided into fourblocks each of which consists of 114 bits. Each block fills one burst inwhole. After the interleaving the signal is modulated, whereafter it istransmitted to the radio path.

The amount of traffic and the number of users continue to increase inradio systems. Since the bandwidth used in radio systems is limited, thenumber of available channels in a radio system is at times insufficientfor all the users to be able to set up a connection. If a connectionfrom a base station to a subscriber terminal, for example, can be setup, the connection may be relatively slow in some cases and thereforetransmission of information takes a long time. The interleaving methodsused in the prior art have not always been sufficiently effective sothat the capacity and data rate in the radio system could be increasedin an easy manner.

BRIEF DESCRIPTION OF THE INVENTION

The purpose of the invention is to implement a multiplexing method and atransceiver realizing the method, such that the aforementioned problemscan be solved. This is achieved with a multiplexing method of the typedescribed in the introduction, characterized by multiplexing at leasttwo blocks together, followed by modulating said blocks into the sametime slot with a modulation method that is adapted to the number of theblocks to be modulated, and transmitting the modulated blocks as acommunication signal in a time slot, so that the transmission speed ofthe communication signal and the number of the connections to beestablished can be increased.

The invention also relates to a transceiver that is used in a TDMA radiosystem and that sets up a connection to another transceiver bytransmitting modulated signals in time slots, and that receives a signalconsisting of bits, and that comprises coding means for channel-codingthe received signal into channel-coded signals, and interleaving meansfor interleaving each channel-coded signal into blocks of apredetermined size.

The transceiver according to the invention is characterized in that thetransceiver comprises multiplexing means that receive blocks from theinterleaving means and that multiplex at least two blocks together, andmodulation means that modulate said blocks based on the number of theblocks to be multiplexed, whereafter the modulated blocks aretransmitted as a communication signal in a time slot, so that thetransmission speed of the communication signal and the number of theconnections to be established can be increased.

The preferred embodiments of the invention are disclosed in thedependent claims.

The basic idea of the invention is that the transceiver multiplexes theinterleaved signal blocks, so that when the blocks are modulated by amultilevel modulation method, several signal blocks can be transmittedin the same burst. The transceiver also demodulates the signal it hasreceived from the radio path by a multilevel modulation method andperforms demultiplexing so that the signal blocks that were in the sameburst can be interleaved again.

The multiplexing method and the transceiver according to the inventionprovide several advantages. The method makes it possible to increase thedata rate of a signal used over a connection between two transceivers.The method also enables an increase in the number of subscriberterminals, for example. The structure of the transceiver does not haveto be modified greatly, but the presently used structural parts can beutilized mostly without any changes.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in greater detail in connection with thepreferred embodiments with reference to the appended drawings, in which

FIG. 1 shows a prior art transceiver,

FIG. 2 shows the structure of a burst,

FIG. 3 shows the placement of prior art signal blocks in bursts,

FIG. 4 shows a transceiver according to the invention,

FIG. 5 shows, in greater detail, a transceiver according to theinvention,

FIG. 6 shows a burst formed by a transceiver according to the invention,

FIG. 7 shows an example of a multiplexing table for signal blocks,

FIG. 8 shows another example of a multiplexing table for signal blocks,

FIG. 9 shows a radio system utilizing the multiplexing method accordingto the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a prior art transceiver. The transceiver comprises speechcoding means 10, channel coding means 20, interleaving means 30,modulation means 40, speech decoding means 70, channel decoding means80, deinterleaving means 90 and demodulation means 100. The transceiveralso comprises an antenna 50 that operates in practice as a transceivingantenna. The speech coding means 10, the channel coding means 20, theinterleaving means 30 and the modulation means 40 constitute thetransmitting end of the transceiver. The speech decoding means 70, thechannel decoding means 80, the deinterleaving means 90 and thedemodulation means 100 form the receiving end of the transceiver.

FIG. 2 shows a burst used in a GSM system. More accurately, the burst isa so-called normal burst where information is transmitted. In a GSMsystem, transmitting a burst requires the capacity of one time slot. Aburst comprises two packets of 57 information bits, a training sequence,two tails of three bits, and two stealing flags of one bit. A burstbegins with three tail bits, which are followed by the first packet of57 information bits, which is followed by a 1-bit stealing flag. Thefollowing sections of the burst include a training sequence of 26 bits,a second stealing flag and a second data packet of 57 information bits.The burst ends with three tail bits.

A prior art transceiver sets up a connection to another transceiver bytransmitting a communication signal in each 57-bit information packet.The speech coding means 10 receive signals that it typically codes intosignals of 260 bits. A 260-bit signal is supplied to the channel codingmeans 20, which code the received signal into a 456-bit signal, which issupplied further to the interleaving means 30. The interleaving means 30interleave the received signal in a known manner. The interleaving means30 form four 114-bit signal blocks from the 456 bits. Each 114-bit blockis supplied to the modulation means 40 that modulate the signal intoeach information packet. Next, the modulated signal is transmitted viathe antenna 50 to another transceiver.

In a prior art transceiver, four bursts are needed to transmit all theinformation from one 456-bit channel-coded signal that is formed intofour 114-bit signal blocks. FIG. 3 shows the placement of prior artsignal blocks in bursts. The figure clearly shows that at least fourbursts are required in order that all four 114-bit blocks could beforwarded to the radio path.

FIG. 4 shows a transceiver 150 according to the invention. Thetransceiver comprises speech coding means 10, channel coding means 20,interleaving means 30, multiplexing means 35 and modulation means 40.The aforementioned means 10, 20, 30, 40 form the transmitting end of thetransceiver. The transceiver also comprises speech decoding means 70,channel decoding means 80, deinterleaving means 90, demultiplexing means95 and demodulation means 100. The means 70, 80, 90, 95 and 100 form thereceiving end of the transceiver. The transceiver also comprises anantenna 50 that operates in practice as a transceiving antenna.

As regards the speech coding means 10, the channel coding means 20, theinterleaving means 30, the decoding means 70, the channel decoding means80 and the deinterleaving means 90, the arrangement according to theinvention operates in the same way as a prior art transceiver. Thecoding means 10 code a signal it has received into 260-bit signals andthe coded signal is supplied to the channel coding means 20, which codethe 260-bit signal further into a 456-bit signal. The signal coded intothe 456-bit form is supplied to the interleaving means 30 thatinterleave the received signal in a known manner. The interleaving means30 form four 114-bit signal blocks from the 456-bit signal it hasreceived.

The signal blocks formed by the interleaving means 30 are supplied tothe multiplexing means 35, which multiplex at least two 114-bit signalblocks that have been interleaved by the interleaving means 30 fortransmission in the same burst. These two signal blocks may be formed ofthe same or different 456-bit channel-coded signals. The interleavedblocks can be transmitted in the same burst since the modulation means40 use multilevel modulation. The modulation means 40 modulate thesignals by a modulation method of at least four levels. The number ofmodulation levels used is preferably exactly four.

In the direction of reception, the transceiver receives with the antenna50 a burst that comprises an information block having the length ofpreferably two 114-bit signals. The demodulation means 100 demodulatethe received signal burst that is supplied further to the demultiplexingmeans 95, and the blocks that were in the same burst are reorganised.The signals are supplied from the multiplexing means 95 to theinterleaving means 90 that reorganise the bits in the blocks. Theinterleaving means 90 form 456-bit signals that are supplied to thechannel decoding means 80, which decode each received 456-bit signalinto a 260-bit signal.

FIG. 5 shows, in greater detail, a transceiver according to theinvention. The transceiver comprises two channel coding means 20 each ofwhich receives a 260-bit signal. One coding means 20 codes the receivedsignal into signal C0 and the other coding means 20 codes the receivedsignal into signal C1. It can be assumed that the coding into signal C0is carried out prior to the coding into signal C1. Each coding means 20codes the received signal into a 456-bit signal. Thereafter, each456-bit signal is supplied into separate interleaving means 30 that formtwo 4-signal blocks from the signals, each block having a length of 114bits. The 114-bit blocks are supplied to the multiplexing means 35,which multiplex the blocks such that one and the same burst may comprise114-bit blocks that are formed of only one or both of the 456-bitsignals.

FIG. 6 shows a burst formed by a transceiver according to the invention.The figure shows that information contained in two 114-bit blocks istransmitted simultaneously in the burst. This means in practice that thetransmission speed of the signal used over the connection and the numberof connections to be set up can be increased. The figure also shows thatthe burst comprises four 1-bit stealing flags.

FIG. 7 shows an example of a multiplexing table for signal blocks. Thefigure shows that the multiplexing means 35 multiplex 114-bit blocksformed of two different 456-bit signals into the burst. For example, themultiplexing means 35 multiplex block one of signal C0 and block threeof signal C1 into a burst denoted by zero. Block two of signal C0 andblock four of signal C1 are multiplexed into burst number one. Whenblock four of signal C1 has been multiplexed, all four blocks of signalC1 have been multiplexed.

The multiplexing means 35 also multiplex block three of signal C0 andblock one of signal C1 into a burst denoted by two. Block four of signalC0 and block two of signal C1 are multiplexed into burst number three.When block four of signal C0 has been multiplexed, all four blocks ofsignal C0 have been multiplexed. The multiplexing method thus enablesthe doubling of the data rate.

The figure shows that the multiplexing processes of the blocks ofsignals C0 and C1 are on a mutual time shift having a length of twoblocks. When the multiplexing means 35 multiplex blocks formed of twodifferent channel-coded signals, the multiplexing means 35 postpone thebeginning of the multiplexing of blocks of one signal by half of theduration of the channel-coded signal. This is clearly shown in FIG. 7,where blocks one and three of two different channel-coded signals aremultiplexed into burst number zero, i.e. the multiplexing of the blockof one signal has been postponed by two blocks. In such a situation, thelength of the channel-coded signal is four blocks, half of which is twoblocks.

FIG. 8 shows another example of a multiplexing table for signal blocks.The figure shows that the multiplexing means 35 multiplex two 114-bitblocks formed of the same 456-bit signal into a burst. The multiplexingmeans 35 multiplex for example the two first blocks of the four blocksof signal C0 into a burst denoted by zero. The multiplexing meansmultiplex the rest of the blocks of signal C0 into burst number two, andall four blocks of signal C0 have thus been multiplexed.

The multiplexing means 35 also multiplex the first two blocks of thefour blocks of signal C1 into a burst denoted by one. The last two114-bit blocks of signal C1 are multiplexed into a burst denoted byfour. The multiplexing method of FIG. 8 makes it possible to double thenumber of connections. The multiplexing means 35 may also multiplex theblocks in a different manner from the above-described tables.

FIG. 9 shows a radio system utilizing the multiplexing method accordingto the invention. The radio system comprises a base station controller300, a base station 101 and a number of subscriber terminals 201 thatmay be mobile phones, for example. The base station 101 and thesubsicber terminal 201 also comprise a transceiver 150, which utilizesthe multiplexing method according to the invention. The multiplexingmeans 35 and the modulation means 40 may be implemented for example withan ASIC.

The advantageous multiplexing method used by the transceiver makes itpossible to increase the channel capacity in the radio system. Thismeans in practice that the number of subscriber terminals 201 can beincreased for example to a double compared to the previous methods.Also, the data rate used over a connection between a base station and asubscriber terminal can be increased with the present multiplexingmethod and with a modulation method that has been selected suitably.

Even though the invention is described above with reference to anexample according to the accompanying drawings, it is clear that theinvention is not restricted thereto but it can be modified in severalways within the scope of the inventive idea disclosed in the appendedclaims.

What is claimed is:
 1. A multiplexing method used in a TDMA radiosystem, in which method connections are set up by means of signals thatare transmitted in time slots and that are modulated before thetransmission, and wherein a signal consisting of bits is received andchannel-coded into channel-coded signals each of which is interleavedinto blocks of a predetermined size, the method comprising: multiplexingat least two blocks together; modulating said at least two blocks intothe same time slot with a modulation method that is adapted to thenumber of the blocks to be modulated; and transmitting the modulatedblocks as a communication signal in the time slot, so that thetransmission speed of the communication signal and the number of theconnections to be established can be increased; wherein when the blocksto be multiplexed are formed at different times, the blocks of twodifferent channel-coded signals are multiplexed preferably such that theblock formed first in the first signal and the block formed third in thesecond signal are modulated for transmission in the same time slot.
 2. Amultiplexing method used in a TDMA radio system, in which methodconnections are set up by means of signals that are transmitted in timeslots and that are modulated before the transmission, and wherein asignal consisting of bits is received and channel-coded intochannel-coded signals each of which is interleaved into blocks of apredetermined size, the method comprising: multiplexing at least twoblocks together; modulating said at least two blocks into the same timeslot with a modulation method that is adapted to the number of theblocks to be modulated; and transmitting the modulated blocks as acommunication signal in the time slot, so that the transmission speed ofthe communication signal and the number of the connections to beestablished can be increased; wherein blocks formed of two differentchannel-coded signals are multiplexed such that the beginning of themultiplexing of blocks of one signal is postponed by half of theduration of the channel-coded signal.
 3. A multiplexing method used in aTDMA radio system, in which method connections are set up by means ofsignals that are transmitted in time slots and that are modulated beforethe transmission, and wherein a signal consisting of bits is receivedand channel-coded into channel-coded signals each of which isinterleaved into blocks of a predetermined size, the method comprising:multiplexing at least two blocks together; modulating said at least twoblocks into the same time slot with a modulation method that is adaptedto the number of the blocks to be modulated; and transmitting themodulated blocks as a communication signal in the time slot, so that thetransmission speed of the communication signal and the number of theconnections to be established can be increased; wherein blocks formed oftwo different channel-coded signals are multiplexed such that thebeginning of the multiplexing of blocks of one signal is postponed bytwo blocks.
 4. A multiplexing method used in a TDMA radio system, inwhich method connections are set up by means of signals that aretransmitted in time slots and that are modulated before thetransmission, and wherein a signal consisting of bits is received andchannel-coded into channel-coded signals each of which is interleavedinto blocks of a predetermined size, the method comprising: multiplexingat least two blocks together; modulating said at least two blocks intothe same time slot with a modulation method that is adapted to thenumber of the blocks to be modulated; and transmitting the modulatedblocks as a communication signal in the time slot, so that thetransmission speed of the communication signal and the number of theconnections to be established can be increased; wherein a multilevelmodulation method is used if more than two blocks are modulated into thesame time slot.
 5. A multiplexing method used in a TDMA radio system, inwhich method connections are set up by means of signals that aretransmitted in time slots and that are modulated before thetransmission, and wherein a signal consisting of bits is received andchannel-coded into channel-coded signals each of which is interleavedinto blocks of a predetermined size, the method comprising: multiplexingat least two blocks together; modulating said at least two blocks intothe same time slot with a modulation method that is adapted to thenumber of the blocks to be modulated; and transmitting the modulatedblocks as a communication signal in the time slot, so that thetransmission speed of the communication signal and the number of theconnections to be established can be increased; wherein a four-levelmodulation method is used if two blocks are modulated into the same timeslot.
 6. A transceiver that is used in a TDMA radio system and sets up aconnection to another transceiver by transmitting modulated signals intime slots and that receives a signal consisting of bits, and thatcomprises coding means for channel-coding the received signal intochannel-coded signals, interleaving means for interleaving eachchannel-coded signal into blocks of a predetermined size, thetransceiver comprising: multiplexing means that receive blocks from theinterleaving means and that multiplex at least two blocks together inthe same timeslot; and modulation means that modulate said at least twoblocks based on the number of the blocks to be modulated, whereafter themodulated blocks are transmitted as a communication signal in the timeslot, so that the transmission speed of the communication signal and thenumber of the connections to be established can be increased; whereinblocks interleaved by the interleaving means are formed at differenttimes, and the multiplexing means multiplexes the blocks of twodifferent channel-coded signals such that the block formed first in thefirst channel-coded signal and the block formed third in the secondchannel-coded signal are multiplexed into the same time slot.
 7. Atransceiver that is used in a TDMA radio system and sets up a connectionto another transceiver by transmitting modulated signals in time slotsand that receives a signal consisting of bits, and that comprises codingmeans for channel-coding the received signal into channel-coded signals,interleaving means for interleaving each channel-coded signal intoblocks of a predetermined size, the transceiver comprising: multiplexingmeans that receive blocks from the interleaving means and that multiplexat least two blocks together in the same timeslot; and modulation meansthat modulate said at least two blocks based on the number of the blocksto be modulated, whereafter the modulated blocks are transmitted as acommunication signal in the time slot, so that the transmission speed ofthe communication signal and the number of the connections to beestablished can be increased; wherein the multiplexing means multiplexesthe blocks of two different channel-coded signals, the multiplexingmeans postpones the beginning of the multiplexing of blocks of onechannel-coded signal by half of the duration of the channel-codedsignal.
 8. A transceiver that is used in a TDMA radio system and sets upa connection to another transceiver by transmitting modulated signals intime slots and that receives a signal consisting of bits, and thatcomprises coding means for channel-coding the received signal intochannel-coded signals, interleaving means for interleaving eachchannel-coded signal into blocks of a predetermined size, thetransceiver comprising: multiplexing means that receive blocks from theinterleaving means and that multiplex at least two blocks together inthe same timeslot; and modulation means that modulate said at least twoblocks based on the number of the blocks to be modulated, whereafter themodulated blocks are transmitted as a communication signal in the timeslots, so that the transmission speed of the communication signal andthe number of the connections to be established can be increased;wherein the multiplexing means multiplexes the blocks of two differentchannel-coded signals, the multiplexing means postpones the beginning ofthe multiplexing of blocks of one channel-coded signal by two blocks. 9.A transceiver that is used in a TDMA radio system and sets up aconnection to another transceiver by transmitting modulated signals intime slots and that receives a signal consisting of bits, and thatcomprises coding means for channel-coding the received signal intochannel-coded signals, interleaving means for interleaving eachchannel-coded signal into blocks of a predetermined size, thetransceiver comprising: multiplexing means that receive blocks from theinterleaving means and that multiplex at least two blocks together inthe same timeslot; and modulation means that modulate said at least twoblocks based on the number of the blocks to be modulated, whereafter themodulated blocks are transmitted as a communication signal in the timeslot, so that the transmission speed of the communication signal and thenumber of the connections to be established can be increased; whereinthe modulation means modulates more than two blocks into the same timeslot with a multilevel modulation method.
 10. A transceiver that is usedin a TDMA radio system and sets up a connection to another transceiverby transmitting modulated signals in time slots and that receives asignal consisting of bits, and that comprises coding means forchannel-coding the received signal into channel-coded signals,interleaving means for interleaving each channel-coded signal intoblocks of a predetermined size, the transceiver comprising: multiplexingmeans that receive blocks from the interleaving means and that multiplexat least two blocks together in the same timeslot; and modulation meansthat modulate said at least two blocks based on the number of the blocksto be modulated, whereafter the modulated blocks are transmitted as acommunication signal in the time slot, so that the transmission speed ofthe communication signal and the number of the connections to beestablished can be increased; wherein the modulation means modulates twoblocks into the same time slot with a four-level modulation method.